Linerless plastic closure

ABSTRACT

An improved linerless plastic closure includes a top panel that has external and internal surfaces and a generally cylindrical sidewall that is unitary with the top panel and has an internally threaded surface that is adapted to engage with a threaded finish portion of a container. A shoulder portion is defined between the internal surface of the top panel and the internal surface of the sidewall. A linerless sealing member extends radially inwardly from the shoulder portion. A first radius is defined in the shoulder portion between the linerless sealing member and the internal surface of the top panel. A second radius is defined in the shoulder portion between the linerless sealing member and the internal surface of the sidewall. But the first and second radii are preferably configured to be at least 0.020 inches, which has been found to reduce the potential for stress-related cracking.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to closures and, more particularly, toplastic linerless closures.

2. Description of the Related Technology

Over the past few decades, the packaging industry has embraced plasticlinerless closures to replace conventional metal closures for suchapplications as hermetic and vacuum applications in the food industryand for use in packaging carbonated beverages.

An important application of plastic linerless closures is the beverageindustry, such as for packaging pressurized water. Attempts have beenmade to replace metal closures which are conventional in the beverageindustry with a plastic linerless closure. Plastic closures aregenerally preferred over metal closures for a number of reasons. Forexample, plastic closures are considered safer than metal closures inthat the possibility of the user being cut during handling the closureis eliminated. Plastic closures may be less likely to blow off from apressurized beverage container and are able to withstand consumermishandling to a much greater extent than are metal closures. Plasticclosures may be molded, making it easy to integrate features such asventilation and areas that are designed to frictionally engage thethreading of the container finish in order to brake the closure as it isbeing removed from the container.

The first generation of plastic closures typically utilized acompressible liner in order to compensate for possible roughness orunevenness on the top rim of the container finish. The pressure createdby the torque of application would compress the liner until its surfacewould conform to the contour of the bottle rim to provide the desiredseal. More recently, however, second-generation linerless closures havebeen developed featuring integral sealing gaskets that are compressed onthe closure is secured to a container. These integral gaskets or sealingmembers are often more effective than the compressible sealing linersthat were used in lined closures. Moreover, linerless closures aregenerally preferred in that they are more economical in manufacture.They are also preferable to lined closures in the context of recycling.

An example of a linerless closure 10 is depicted in FIG. 1. Closure 10included a top panel 12 having an exterior upper surface and an interiorlower surface, and a generally cylindrical sidewall 14 having anexternal surface and internal surface upon which at least one interiorthreaded 16 is defined. A thickened shoulder portion 18 is defined wherethe top panel 12 joins the sidewall 14, and a linerless sealing member20 extends radially inwardly and downwardly from the shoulder portion18. A first radius R1 _(P) is defined in the shoulder portion 18 betweenthe linerless sealing member 20 and the interior surface of the toppanel 12. A second radius R2 _(P) is defined in the shoulder portion 18between the linerless sealing member 20 and the interior surface ofsidewall 14. In this particular closure, both the first and second radiiwere constructed to be about 0.10 inches.

Unfortunately, closures such as that described with reference to FIG. 1were found in practice to be more susceptible to stress-related damagethan was desirable, which often led to small cracks developing withinthe closure. Closures fabricated from high-density polyethylene wereespecially susceptible to such failure, which was disappointingconsidering this material has substantial advantages over alternativematerial such as polypropylene. These advantages include better tastecharacteristics and superior sealing properties.

A need clearly existed for an improved linerless closure that wouldprovide the substantial benefits of a linerless closure but that is lesslikely to suffer from stress-related cracking and related degradationthan was existing conventional linerless closures.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide an improvedlinerless closure that delivers the substantial benefits of a linerlessclosure but that is less likely to suffer from stress-related crackingand related degradation than was existing conventional linerlessclosures.

In order to achieve the above and other objects of the invention, alinerless closure that is constructed according to a first aspect of theinvention includes a top panel having external and internal surfaces; agenerally cylindrical sidewall that is unitary with the top panel andhas a threaded internal surface; a shoulder portion defined between theinternal surface of the top panel and the internal surface of thesidewall; a linerless sealing member extending radially inwardly fromthe shoulder portion; a first radius defined in the shoulder portionbetween the linerless sealing member and the internal surface of the toppanel; and a second radius defined in the shoulder portion between thelinerless sealing member and the internal surface of the sidewall, andwherein both the first radius and the second radius are at least 0.020inches.

An improved linerless plastic closure according to a second aspect ofthe invention includes a top panel having external and internalsurfaces; a generally cylindrical sidewall, the sidewall being unitarywith the top panel and having a threaded internal surface; a shoulderportion defined between the internal surface of the top panel and theinternal surface of the sidewall; a linerless sealing member extendingradially inwardly from the shoulder portion; a first radius defined inthe shoulder portion between the linerless sealing member and theinternal surface of the top panel; and a second radius defined in theshoulder portion between the linerless sealing member and the internalsurface of the sidewall, and wherein the first radius is at least 0.020inches.

An improved linerless plastic closure according to a third aspect of theinvention includes a top panel having external and internal surfaces; agenerally cylindrical sidewall, the sidewall being unitary with the toppanel and having a threaded internal surface; a shoulder portion definedbetween the internal surface of the top panel and the internal surfaceof the sidewall; a linerless sealing member extending radially inwardlyfrom the shoulder portion; a first radius defined in the shoulderportion between the linerless sealing member and the internal surface ofthe top panel; and a second radius defined in the shoulder portionbetween the linerless sealing member and the internal surface of thesidewall, and wherein the second radius is at least 0.020 inches.

An improved linerless plastic closure according to a fourth aspect ofthe invention preferably includes a top panel having external andinternal surfaces; a generally cylindrical sidewall that is unitary withthe top panel and has a threaded internal surface; a linerless sealingmember extending radially inwardly from an area that is adjacent to anarea of connection between the sidewall and the top panel; a firstradius defined between the linerless sealing member and the internalsurface of the top panel; and a second radius defined between thelinerless sealing member and the internal surface of said sidewall, andwherein the first radius is at least 0.020 inches.

An improved linerless plastic closure according to a fifth aspect of theinvention preferably includes a top panel having external and internalsurfaces; a generally cylindrical sidewall that is unitary with the toppanel and has a threaded internal surface; a linerless sealing memberextending radially inwardly from an area that is adjacent to an area ofconnection between the sidewall and the top panel; a first radiusdefined between the linerless sealing member and the internal surface ofthe top panel; and a second radius defined between the linerless sealingmember and the internal surface of said sidewall, and wherein the secondradius is at least 0.020 inches.

These and various other advantages and features of novelty thatcharacterize the invention are pointed out with particularity in theclaims annexed hereto and forming a part hereof. However, for a betterunderstanding of the invention, its advantages, and the objects obtainedby its use, reference should be made to the drawings which form afurther part hereof, and to the accompanying descriptive matter, inwhich there is illustrated and described a preferred embodiment of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatical cross-sectional view of a conventionallinerless plastic closure; and

FIG. 2 is a diagrammatical cross-sectional view of a linerless plasticclosure that is constructed according to a preferred embodiment of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring now to the drawings, wherein like reference numerals designatecorresponding structure throughout the views, and referring inparticular to FIG. 2, an improved linerless plastic closure 30 that isconstructed according to a preferred embodiment of the inventionincludes a top panel 32 having an upper external surface 34 and a lower,internal surface 36. Top panel 32 is unitary with a downwardly dependinggenerally cylindrical sidewall 38 that has an exterior surface 40 andinternal surface 42 that has at least one thread 44 defined thereon forengaging with an external threaded surface of the finish portion of acontainer.

Closure 30 is preferably fabricated from high-density polyethylene,which provides taste advantages and advantages in sealing propertieswith respect to alternative materials such as polypropylene.

A thickened shoulder region 46 is defined proximate the area wheresidewall 38 joins top panel 32. Shoulder region 46 is preferably thickerin a radial direction than an average thickness of sidewall 38, and isalso preferably thicker in a longitudinal, axial direction than anaverage thickness of top panel 32. Extending radially inwardly andslightly downwardly from shoulder portion 46 is a flexible linerlesssealing member 48. The interior surface of shoulder portion 46 andflexible linerless sealing member 48 are preferably constructed so thatthey extend in annular fashion so as to have a regular cross-sectionthroughout the entire axis of rotation of the closure 30.

An annular pressure rim 50 is preferably defined on the internal surface36 of the top panel 32 to aid in sealing when the closure 30 is securelymounted upon a container.

According to one advantageous aspect of the invention, a first radius R1is defined in an internal surface of the shoulder region 46 between thelinerless sealing member 48 and the internal surface 36 of top panel 32.First radius R1 intersects the internal surface 36 of the top panel 32,as is shown in FIG. 2. First radius R1 is preferably at least 0.020inches, and is preferably within a range of about 0.020 inches to about0.036 inches. More preferably, first radius R1 is within a range ofabout 0.023 inches to about 0.030 inches.

A second radius R2 is also advantageously defined in the internalsurface of the shoulder region 46 between the linerless sealing member48 and the internal surface 42 of the sidewall 38. Second radius R2intersects the internal surface 42 of the sidewall 38, as is shown inFIG. 2. Second radius R2 is preferably at least 0.020 inches, and ispreferably within a range of about 0.020 inches to about 0.036 inches.More preferably, second radius R2 is within a range of about 0.023inches to about 0.030 inches.

The first and second radii R1, R2 may be although not necessarily aresubstantially the same dimension.

Closure 30 has been found to exhibit significantly improved resistanceto stress-related cracking with respect to the conventional closurestructure that is discussed above with reference to FIG. 1.

It is to be understood, however, that even though numerouscharacteristics and advantages of the present invention have been setforth in the foregoing description, together with details of thestructure and function of the invention, the disclosure is illustrativeonly, and changes may be made in detail, especially in matters of shape,size and arrangement of parts within the principles of the invention tothe full extent indicated by the broad general meaning of the terms inwhich the appended claims are expressed.

1. An improved linerless plastic closure, comprising: a top panel havingexternal and internal surfaces; a generally cylindrical sidewall, saidsidewall being unitary with said top panel and having a threadedinternal surface; a shoulder portion defined between said internalsurface of said top panel and said internal surface of said sidewall; alinerless sealing member extending radially inwardly from said shoulderportion; a first radius defined in said shoulder portion between saidlinerless sealing member and said internal surface of said top panel;and a second radius defined in said shoulder portion between saidlinerless sealing member and said internal surface of said sidewall, andwherein both said first radius and said second radius are at least 0.020inches.
 2. An improved linerless plastic closure according to claim 1,wherein both said first radius and said second radius are within a rangeof about 0.020 inches to about 0.036 inches.
 3. An improved linerlessplastic closure according to claim 2, wherein both said first radius andsaid second radius are within a range of about 0.023 inches to about0.030 inches.
 4. An improved linerless plastic closure according toclaim 2, wherein said first radius is within a range of about 0.023inches to about 0.030 inches.
 5. An improved linerless plastic closureaccording to claim 2, wherein said second radius is within a range ofabout 0.023 inches to about 0.030 inches.
 6. An improved linerlessplastic closure according to claim 1, wherein said closure is fabricatedfrom high-density polyethylene.
 7. An improved linerless plastic closureaccording to claim 1, wherein said shoulder portion is thicker in aradial direction than an average radial thickness of said sidewall. 8.An improved linerless plastic closure according to claim 1, wherein saidshoulder portion is thicker in a longitudinal direction than an averagelongitudinal thickness of said top panel.
 9. An improved linerlessplastic closure according to claim 1, wherein said first radius issubstantially equal to said second radius.
 10. An improved linerlessplastic closure according to claim 1, wherein said first radiusintersects said internal surface of said top panel
 11. An improvedlinerless plastic closure according to claim 1, wherein said secondradius intersects said internal surface of said sidewall.
 12. Animproved linerless plastic closure, comprising: a top panel havingexternal and internal surfaces; a generally cylindrical sidewall, saidsidewall being unitary with said top panel and having a threadedinternal surface; a shoulder portion defined between said internalsurface of said top panel and said internal surface of said sidewall; alinerless sealing member extending radially inwardly from said shoulderportion; a first radius defined in said shoulder portion between saidlinerless sealing member and said internal surface of said top panel;and a second radius defined in said shoulder portion between saidlinerless sealing member and said internal surface of said sidewall, andwherein said first radius is at least 0.020 inches.
 13. An improvedlinerless plastic closure according to claim 12, wherein said firstradius is within a range of about 0.020 inches to about 0.036 inches.14. An improved linerless plastic closure according to claim 13, whereinsaid first radius is within a range of about 0.023 inches to about 0.030inches.
 15. An improved linerless plastic closure according to claim 12,wherein said closure is fabricated from high-density polyethylene. 16.An improved linerless plastic closure according to claim 12, whereinsaid shoulder portion is thicker in a radial direction than an averageradial thickness of said sidewall.
 17. An improved linerless plasticclosure according to claim 12, wherein said shoulder portion is thickerin a longitudinal direction than an average longitudinal thickness ofsaid top panel.
 18. An improved linerless plastic closure according toclaim 12, wherein said first radius intersects said internal surface ofsaid top panel
 19. An improved linerless plastic closure according toclaim 12, wherein said second radius intersects said internal surface ofsaid sidewall.
 20. An improved linerless plastic closure, comprising: atop panel having external and internal surfaces; a generally cylindricalsidewall, said sidewall being unitary with said top panel and having athreaded internal surface; a shoulder portion defined between saidinternal surface of said top panel and said internal surface of saidsidewall; a linerless sealing member extending radially inwardly fromsaid shoulder portion; a first radius defined in said shoulder portionbetween said linerless sealing member and said internal surface of saidtop panel; and a second radius defined in said shoulder portion betweensaid linerless sealing member and said internal surface of saidsidewall, and wherein said second radius is at least 0.020 inches. 21.An improved linerless plastic closure according to claim 20, whereinsaid second radius is within a range of about 0.020 inches to about0.036 inches.
 22. An improved linerless plastic closure according toclaim 21, wherein said second radius is within a range of about 0.023inches to about 0.030 inches.
 23. An improved linerless plastic closureaccording to claim 20, wherein said closure is fabricated fromhigh-density polyethylene.
 24. An improved linerless plastic closureaccording to claim 20, wherein said shoulder portion is thicker in aradial direction than an average radial thickness of said sidewall. 25.An improved linerless plastic closure according to claim 20, whereinsaid shoulder portion is thicker in a longitudinal direction than anaverage longitudinal thickness of said top panel.
 26. An improvedlinerless plastic closure according to claim 20, wherein said firstradius intersects said internal surface of said top panel
 27. Animproved linerless plastic closure according to claim 20, wherein saidsecond radius intersects said internal surface of said sidewall.
 28. Animproved linerless plastic closure, comprising: a top panel havingexternal and internal surfaces; a generally cylindrical sidewall, saidsidewall being unitary with said top panel and having a threadedinternal surface; a linerless sealing member extending radially inwardlyfrom an area that is adjacent to an area of connection between saidsidewall and said top panel; a first radius defined between saidlinerless sealing member and said internal surface of said top panel;and a second radius defined between said linerless sealing member andsaid internal surface of said sidewall, and wherein said first radius isat least 0.020 inches.
 29. An improved linerless plastic closureaccording to claim 28, wherein said first radius is within a range ofabout 0.020 inches to about 0.036 inches.
 30. An improved linerlessplastic closure according to claim 29, wherein said first radius iswithin a range of about 0.023 inches to about 0.030 inches.
 31. Animproved linerless plastic closure according to claim 28, wherein saidclosure is fabricated from high-density polyethylene.
 32. An improvedlinerless plastic closure according to claim 28, wherein said secondradius is also at least 0.020 inches.
 33. An improved linerless plasticclosure according to claim 32, wherein both said first and second radiiare within a range of about 0.020 inches to about 0.036 inches.
 34. Animproved linerless plastic closure according to claim 33, wherein bothsaid first and second radii are within a range of about 0.023 inches toabout 0.030 inches
 35. An improved linerless plastic closure,comprising: a top panel having external and internal surfaces; agenerally cylindrical sidewall, said sidewall being unitary with saidtop panel and having a threaded internal surface; a linerless sealingmember extending radially inwardly from an area that is adjacent to anarea of connection between said sidewall and said top panel; a firstradius defined between said linerless sealing member and said internalsurface of said top panel; and a second radius defined between saidlinerless sealing member and said internal surface of said sidewall, andwherein said second radius is at least 0.020 inches.
 36. An improvedlinerless plastic closure according to claim 35, wherein said secondradius is within a range of about 0.020 inches to about 0.036 inches.37. An improved linerless plastic closure according to claim 36, whereinsaid second radius is within a range of about 0.023 inches to about0.030 inches.
 38. An improved linerless plastic closure according toclaim 35, wherein said closure is fabricated from high-densitypolyethylene.